Global positioning system, abbreviated GPS, is the plan of precise satellite navigation system developed by the United States, and the GPS includes 26 satellite vehicles distributed and operated among six orbits, and each orbit has approximately 55 degrees inclination with respect to Earth's equator, such that an operator using GPS on Earth can receive the signals from 4˜8 satellites anytime and anywhere, if the signals are not blocked by terrain or construction, regardless of weather conditions and calculate current position based on the signals. With such space technology, any operator using GPS can obtain accurate his own location, speed and local time easily.
The GPS development project was held by the U.S. Department of Defense for military purpose in beginning. With participation of the U.S. Department of Transportation, the technology was transferred for civilian use and applied in operations such as navigation and positioning, precision measurement and standard time. GPS is a navigation system that integrates satellite and wireless technologies to provide a user's precise location, speed and local time. GPS is used extensively, and many GPS technologies and business opportunities are developed rapidly as satellite technologies advance. At early stage, GPS was intended for military units and used for military purposes such as the precision positioning of air fighters, ships, motor vehicles, staffs and targets. Till now, GPS is free for civilian use and applied in the positioning, and such technology of integrating the space satellites and the communication technology is developed rapidly. In addition to the precise positioning function, the GPS also can be added on more functionality to provide accurate information of speed, direction and distance. The applicability scope of GPS is very extensive, and thus it creates lots of business opportunities.
However, the navigation equipments for GPS must be located in an open area where the sky and surroundings do not have any obstacle to receive satellite signals transmitted from a GPS satellite by a GPS antenna to download ephemeris data. After obtaining sufficient ephemeris data, the navigation equipments can complete a first-time positioning, and the aforementioned process is called “Cold Start”. The positioning process usually takes about 45 seconds to 2 minutes, or more time for regions with a poor signal reception.
However, the downloaded GPS ephemeris data is time-sensitive, because the GPS satellites in the sky are not fixed, and the same GPS satellite travels around the world twice per day. For example, all GPS ephemeris data of a SiRF GPS module come with an expiration time about four hours, and if the data is not updated within four hours, then the original GPS ephemeris data will no longer have the value of serving as a reference anymore. Therefore, the navigation equipment must perform a cold start again, but it is time consuming to periodically perform the necessary process of updating GPS ephemeris data.
In recent two years, some designs used a Global System for Mobile Communications (GSM) mobile phone with a general packet radio service (GPRS) for the positioning process. The major difference between a so-called assisted global positioning system (AGPS) and a conventional GPS resides on that the GPS only uses satellites for the positioning process, and the first-time positioning process and each positioning process thereafter take a long time, but the AGPS roughly searches the user's location through the GSM base station first, and then uses GPS satellites for precise positioning. The AGPS not only saves the time for the first-time positioning process, but also reduces the time consumed by the conventional GPS for each positioning thereafter from one minute to ten seconds, and overcomes the existing drawback of unable to receive signals from the satellite indoors.
Although the AGPS can improve the drawback of wasting too much time on updating the ephemeris data of a conventional GPS, yet the AGPC requires a mobile phone with the AGPS function and a telecommunication service which is provided by a telecommunication company. Furthermore, the telecommunication company will charge users for transmitting GPRS packets, and thus an additional cost is incurred.
In view of the drawbacks of the prior art, the inventor of the present invention based on years of experience in the related industry to conduct extensive researches and experiments, and finally invented a positioning system and a control method thereof to expedite the positioning time through this system without incurring additional hardware cost.